Balrogg: Demonically compacting (up to 15%) lossless Vorbis/Opus recompressor

github.com

82 points by palaiologos 3 days ago


tux3 - 13 hours ago

So, it looks like this tries to build a model (or rather, multiple layers of models combined with something called context mixing[0]), potentially analyzing the whole file first? Is it fair to call this a very fancy entropy coder, replacing the last phase of what a traditional audio codec does (the lossless part, after quantization)?

I like the code style, this is pretty nice C. It's refreshing to see human code.

[0]: https://en.wikipedia.org/wiki/Context_mixing

merbanan - 13 hours ago

Vorbis sends the entropy tables in the actual file at the start.

https://www.xiph.org/vorbis/doc/Vorbis_I_spec.html#x1-470003

If you have the complete file you can calculate the optimal ones. In a streaming scenario that does not work and you have use something you think is good.

sinnet3000 - 12 hours ago

The git username sounded familiar, it's from the same developer that created bzip3.

EdSchouten - 13 hours ago

Interesting that it doesn’t use the same open source license as Vorbis/Opus itself. Otherwise improvements like these could be upstreamed?

BoingBoomTschak - 13 hours ago

Those .blr extensions in the examples are making me doubt: the result is still conformant and playable ogg Vorbis/Opus, right?

functionmouse - 7 hours ago

Why was this written with explicit Windows 95 support? Just 'cuz?